The invention relates to a rethermalizing heater or sink heater. The rethermalizing heater or sink heater uses a single tube or multiple tubes with external heating elements in thermally conductive contact with the tube or tubes, providing heat transfer to liquid flowing through the tubes. Liquid is circulated through the tubes and into a tank or sink through the process of thermal siphoning.
Recirculation of water, or other liquids, for example cleaning solutions, is a process commonly used in the food industry. For example, recirculation of wash water has been used in dishwashers. In such a recirculating dishwasher, a tank is used as a relatively large reservoir that is filled with a solution of water and detergent for washing. The water and detergent solution is recycled for washing successive racks with a large percentage of the same liquid being recirculated. The liquid is somewhat diluted with fresh rinse water after each cycle. A drain valve is typically located at the bottom of a tank. Further, an overflow may be located near the top of the tank. The fresh water spray system rinses the racks of dishware at the proper time in a cycle, after it has been washed by pumped recirculation of the large volume of wash water. The wash water is typically heated by a heater that acts as a heat sink to maintain water temperature. Often, such a heater is an electrical heating element submerged in the wash water tank. Using a submerged heating element has the disadvantage that lime and other mineral build-up is caused on the heating element. Such lime and mineral build-up is difficult to remove without the use of chemicals. Furthermore, if the lime and mineral build-up is not frequently removed, the heating element is subject to failure.
Conventionally, rethermalizing heaters used for reheating of bagged food product or sink heaters used for sterilizing dishware use a two tank system. One tank is used to collect debris from the system. The debris collecting tank has a ball valve drain. The other tank contains the heating element or elements and is separated to avoid sludge or debris from collecting in it. The second tank has a removal cap on a small drain. Frequently, however, the tank having the substantially clean solution gets contaminated when the first debris collecting tank is not sufficiently drained and flushed frequently enough or completely enough. Furthermore, limescale build-up or mineral build-up occurs in the heated tank that is difficult to remove without the use of chemicals. When the heated tank gets contaminated with scale or debris, the unit may malfunction and the heating elements are subject to failure. Such frequent failures create a major service problem and an increase in warranty costs due to failures.
Further, conventional rethermalizing or sanitizing heating systems use pumps to recirculate fluid through the heating element and into a fluid tank. Such pumping systems are plagued with mechanical pump failures and require routine pump maintenance.
Accordingly, there is a need for a rethermalizing heater or sink heater that uses a heating element that is not submerged in the solution. Further, there is a need for a rethermalizing heater or sink heater that utilizes a single tank. Further still, there is a need for a rethermalizing heater or sink heater that is easily cleaned and easily drained. Yet Further still, there is a need for a rethermalizing heater or sink heater that does not require the use of chemicals to remove the limescale build-up or mineral build up from heating elements. Still further, there is a need for a rethermalizing or sink heater that does not use a mechanical pump for recirculating fluid.
An exemplary embodiment of the invention relates to a flow heater system for heating fluid. The flow heater system includes a fluid receptacle and a flow tube in fluid communication with the fluid receptacle. The flow heater system also includes a heating element in conductive communication with the flow tube. Fluid flow through the flow tube is caused by thermal siphoning.
Another exemplary embodiment of the invention relates to a sink heater configured to heat and recirculate liquid in a sink. The sink heater includes a flow tube having an inlet and an outlet in fluid communication with the sink. The sink heater also includes a heating element configured to exchange heat with the flow tube. Fluid flow through the tube is caused by convection from the sink into the inlet and out of the outlet into the sink.
Further, an exemplary embodiment of the invention relates to a method for heating liquid in a fluid receptacle. The method includes providing a flow tube in fluid communication with the fluid receptacle. The method also includes providing a fluid in the fluid receptacle. Further, the method includes providing a heating element in conductive communication with the flow tube. Further still, the method includes controlling current through the heating element and creating a thermal siphoning effect in the flow tube.